Hydrocarbon fuels



United States Patent HYDROCARBON FUELS Edmund L. Niedzielski, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application September 4, 1956 Serial No. 607,568

18 Claims. (Cl. 52.5)

This invention relates to hydrocarbon fuels which contain novel carbon-burning catalysts.

The accumulation of carbonaceous deposits in com bustion chambers, resulting from the incomplete combustion of hydrocarbon fuels, is an important factor in lowering the performance of internal combustion engines, jet engines, and oil burners and have other undesirable effects. carbonaceous deposits accumulating in the combustion chamber of an automotive engine promote preignition of the fuel and also increase the octane requirement of the engine. These harmful effects are accentuated by the presence of lead oxides and salts produced in-the combustion of gasoline containing tetraethyl lead. The carbonaceous material acts as a binder for the lead oxides and salts which otherwise would be eliminated from the combustion chamber by mechanical action, and thus is largely responsible for the build-up of deposits of lead compounds in the combustion chamber of spark iginition engines. The accumulation of carbonaceous deposits is most pronounced under light-duty engine operations where the combustion temperatures are relatively low and hence the com bustion of the hydrocarbons is less complete.

In jet engines, the build-up of carbon in the combustion zone interferes with heat transfer and the fuel spray pattern. Also, the flaking of large particles of carbon from such deposits tends to decrease the life of turbine blades. The formation of carbonaceous deposits in the combustion zone of oil burners interferes with heat transfer, restricts air flow, and results in objectionable excessive smoking of the burner.

It is highly desirable to prevent or to minimize the accumulation of carbonaceous deposits in the combustion chambers of engines and burners operating on normally liquid hydrocarbon fuels. This problem has been long recognized in the art and many attempts have been made to solve it but without complete success.

Many metal compounds have been proposed as antiknock agents for gasoline employed in spark ignition engines. However, such agents have little or no effect to minimize the accumulation of carbonaceous deposits in the engines.

It is also known that motor fuels and crankcase oils, employed in spark ignition engines, generally are subject to oxidation, producing gummy materials or sludge which deposits on the piston rings of such engines and are there converted to carbonaceous deposits. It has been common practice to add substances, including some metal compounds, to such motor fuels and oils to stabilize them against oxidation and gum and sludge formation and hence to prevent the formation of carbonaceous deposits by the gum or the sludge. While such practice has alleviated the problem tosome extent, objectionable accumulation of carbonaceous deposits still occurs when the stabilized motor fuels and oils are used. The stabilizers (antioxidants) are not known or recognized to render the combustion of the hydrocarbon more complete or to act as carbon-burning catalysts and, in general, do not so function to-any appreciable extent, their anti-oxidizing action being antagonistic to carbonburning. 1

It has further been proposed to incorporate certain organo-metallic compounds in fuels to function as carbon-burning catalysts and thereby further minimize carbonaceous deposits in combustion chambers of engines and burners; e.g., metal dibutyldithiocarbamates. The activity for this purpose has been attributed to the metals, the organic component functioning to solubilize the metal in the hydrocarbon fuel. These materials, though effective above about 500 C., have little effect in the critical region of BOO-350 C. where the accumulation of carbonaceous deposits is most pronounced. It is an object of this invention to minimize the formation of carbonaceous deposits in the combustion of normally liquid hydrocarbon fuels. A particular object is to provide normally liquid hydrocarbon fuels containing novel efiicient carbon-burning catalysts which materially decrease the quantity of carbonaceous deposits accumulating in the combustion zones of equipment during the combustion of the fuels therein. Other objects are.to provide new compositions of matter and to advance the art.

The above and other objectsv are accomplished by this invention which comprises normally liquid hydrocarbon fuels containing from about 0.01% .to about 1% by weight of a divalent-metal chelate of the group consisting of the cobalt, copper and nickel chelates of salicylaldehyde-nitroanils and the cobaltand copper chelates of malonaldehyde-di-nitroanils, each nitroanil portion of the molecule being an imino radical selected from nitrophenyl imino, alkyl-substituted nitrophenyl imino and lower alkoxy-substituted nitrophenyl imino radicals.

It has been found that the metal chelates, as defined above, are very efiective carbon-burning catalysts in the combustion of the normally liquid hydrocarbon fuels. In other words, when the fuels containing those chelates are burned, the chelates catalyze the combustion of the fuels and of carbon formed during the combustion so that the fuels and the carbon are more completely consumed, whereby the formulation of carbonaceous deposits in the combustion equipment and the formation of soot in the exhaust gases is prevented or is greatly decreased.

A divalent-metal chelate is one in which the metal is in the divalent state. Sometimes hereinafter the divalent state of the metal is indicated by the name of the metal followed by (II), as in cobalt (II) and in salicylal-(3-nitro-4-t-butyl)aniline cobalt (II).

The salicylaldehyde-nitroanils (hereinafter sometimes designated as salicylal-nitroanilines) are Schitfs bases derived from equimolecular proportions of salicylaldehyde and one of nitroaniline, nitroaniline substituted on ring carbon atoms by alkyl groups, and nitroaniline substituted on ring carbon atoms by lower alkoxy groups, by condensation with the elimination of water wherein the carbonyl oxygen of salicylaldehyde is replaced by the a corresponding N-(nitroaromatic)imino radical. Thus, the salicylaldehyde-nitroanils may be represented by the formula:

HO--C H -CH=N-ArNO wherein Ar-NO represents a nitrophenyl, an alkylsubstituted nitrophenyl or a lower alkoxy-substituted nitrophenyl radical.

The malonaldehyde-di-nitroanils (hereinafter some times designated as malonal-di-nitroanilines) are Schitfs bases derived from one mole of malonaldehyde and two moles of one or more of nitroaniline, nitroaniline substituted on ring carbon atoms by alkyl groups, and nitroaniline substituted on ring carbon atoms by lower alkoxy groups, by condensation with the elimination of water wherein each of the carbonyl oxygen atoms of malonaldehyde is replaced by a corresponding N-(nitroaromat-ic)imino radical. The two N-(nitroaromatic)imino radicals may be the same or different. Thus, the malonaldehyde-di-nitroanils may be represented by the formula:

wherein the Ar--NO radicals represent the same or different radicals of the group of nitrophenyl, alkyl-substituted nitrophenyl and lower alkoxy-substituted nitrophenyl radicals.

The presence of the nitro group in the anil portion of the molecule is essential for the purposes of this invention. Analogousmetal chelates, in which the nitro group is not present, are wholly or substantially lacking in carbon-burning activity.

Alkyl or lower alkoxy groups on the benzene ring of the nitroanil confer additional desirable properties to the chelates, including particularly enhanced solubility in the normally liquid hydrocarbon fuels. The alkyl groups may be lower or higher alkyl groups and may be straight chain or branched chain, primary, secondary or tertiary alkyl groups. Preferably, they are branched chain, particularly tertiary alkyl groups. For reasons of cost and economy, the alkyl groups should contain not more than 8 carbon atoms, and preferably contain 48 carbon atoms. Representative alkyl groups are methyl, ethyl, nand iso-propyl, n-, iso-, sec-, and t-butyl, isoamyl, secamyl, t-amyl, octyl, dodecyl, octadecyl, and the like. The preferred alkyl groups are sec-butyl, tert-butyl (t-butyl), sec-amyl, tert-amyl and octyl. Also preferably, the nitroanils are the meta-nitroanils, particularly the 3-nitro-4- alkyl-anils.

The lower alkoxy groups contain 1-4 carbon atoms and are represented by methoxy, ethoxy, propoxy and butoxy groups. The methoxy group is preferred.

The divalent cobalt, copper and nickel chelates of the salicylaldehyde-nitroanils and the divalent cobalt and copper chelates of the malonaldehyde-di-nitroanils of this invention are very effective carbon-burning catalysts. On the other hand, the nickel chelates of the malonaldehydedi-nitroanils appear to have little or no carbon-burning activity, and hence are excluded from this invention. The most effective and preferred metal chelates are: the cobalt (II) chelates of the salicylaldehyde-(3-nitro-4- alkyl)anils in which alkyl represents t-butyl, sec-amyl and octyl, particularly t-butyl; the copper (II) chelate of salicylaldehyde-(3-nitro-4-octyl)anil; and the nickel (II) chelate of salicylaldehyde-(3-nitro-4-octyl)anil.

The anils and the metal chelates thereof may be prepared by conventional methods known in the art. The salicylaldehyde-nitroanils are obtained by reacting equimolar quantities of salicylaldehyde with the desired nitroaromatic primary amine, a mole of water being eliminated in the reaction, as described by Bigelow and Eatough, Org. Synth, Coll. Vol., I, 80 (1941), and by Campbell et al., .J. Am. Chem. Soc., 70, 3868 (1948). The malonaldehyde-dimitroanils are most conveniently prepared, as described in US. Patent No. 2,549,097 for example, by condensing one mole of a malonaldeh-yde diacetal with 2 moles of the desired nitroaromatic primary amine in the presence of mineral acid, followed by treatment With aqueous caustic.

The cobalt, copper and nickel chelates of these anils and dianils, as the case may be, are readily obtained following conventional methods, as described by Bailes and Calvin, J. Am. Chem. Soc. 69, 1886 (1947), and Mantell et al., I. Am. Chem. Soc., 77, 5820 (1955). The intermediate Schitfs base (anils) leading to the chelates of this invention have a replaceable phenolicor eneimine hydrogen. Replacement by a metal may be done directly, by reacting the Schiifs base with the appropriate metal hydroxide, or indirectly by reacting the sodium salt of the anil with the acetate of cobalt, copper or nickel in aqueous alcohol, to effect metal exchange. Or, in a variation of the second method, a stoichiometric mixture of the metal acetate and the Schitfs base in aqueous alcohol is treated with caustic.

The normally liquid hydrocarbon fuels include motor fuels for spark ignition engines, such as gasoline and other hydrocarbons or mixtures of hydrocarbons in the gasoline boiling range which may contain tetraethyl lead or other anti-knock agent; kerosene; and fuel oils such as diesel engine fuel, jet engine fuel, oil-burner fuel, and the like. Such fuels may contain other conventional additives such as dyes, fluorescent agents, color stabilizers, gum or sludge inhibitors, gum or sludge solvents anddispersants, detergents, and the like. While the chelates of this invention show carbon-burning activity in crankcase oils, their use therein is impractical because high concentrations, about 30 to about by Weight, of the chelates are required to decreasethe formation of carbonaceous deposits to a reasonably desired degree, and such high concentrations are impractically uneconomical, seriously affect desirable characteristics of the crankcase oils, such as viscosity, viscosity index, pour point, and the like, and tend to precipitate therefrom and deposit in distributing and feeding systems such as fuel lines, orifices, valves, screens and the like.

Normally, the chelates of this invention will be employed in the normally liquid hydrocarbon fuels in an amount of from about 0.01% to about 1% by Weight based on the fuel. Larger amounts may be used if desired, but materially larger amounts do not provide corresponding increased beneficial results and are uneconomical. The chelates are soluble in such fuels "to the extent of at least 0.01% by weight and, preferably, are employed in solution therein. Also, mixtures of any two or more of the chelates may be used, as desired.

Despite the fact that it is impractical to use the chelates in crankcase oils, it has been found that the most rapid and most economical method for evaluating carbon-burning catalysts involves testing them in lubricating oils by the method described below and illustrated in Examples 1 to 4, inclusive. The results obtainedby such test method correlate with the results obtained when the compounds are employed in normally liquid hydrocarbon fuels in concentrations of about 0.01l% by Weight.

Such test method consists of heating one-gram samples of lubricating oil, with and without a compound to be tested for carbon-burning activity, in an electric furnace at about 300350 C., usually about 300 C., in the presence of a stream of air for about one hour. An airinlet tube leads into the electric furnace. The amount and the rate of flow of air introduced into the furnace is regulated by conventional means, such as a reducing valve and a flow meter. The door of the furnace is left slightly ajar to allow air to escape. A S-deck steel tray is placed in the furnace, and thermocouples, to measure temperature, extend over the top deck of the tray. The oil samples to be tested are contained in porcelain dishes, 4 cm. in diameter, which are placed on the lower four decks of the tray, usually 6 dishes on each of the two lowest decks and 4 dishes on each of the two decks above.

f the 20 samples tested in each experiment, were controls on the lubricating oil without added compound; 5 were controls on the compounds alone (without oil), representing single samples of each of 5 compounds to be evaluated in the experiment; and were duplicate samples of lubricating oil in which each duplicate set contained a difierent individual compound of the five to be evaluated. The samples were arranged in random order on the tray. When it was desired to determine the effect of metal surfaces on the accumulation of carbonaceous deposits, polished aluminum or low-carbon steel discs were fitted into the porcelain dishes. The dishes and the metal discs (when used) were prepared for reuse by beating them in the furnace at 600 C. to burn off any deposits from preceding tests.

It has been found that, at an air flow rate of 10 liters per minute and a temperature of 300 C., the lubricating oils in the dishes were completely destroyed, being largely converted to hard black carbonaceous residues in the absence of efiicient carbon-burning catalysts. These carbonaceous residues closely resemble the deposits formed in automotive engines and are at a maximum at temperatures of 300-350" C., the quantity of residue decreasing as the temperature is increased, in agreement with engine test results which show that the more severe the engine conditions the less the accumulation of carbonaceous deposits in the combustion chamber. All the usual crankcase oils for automotive engines produced typical carbonaceous deposits, and oil forming less carbonaceous residue in this oven test showed a smaller octane requirement increase in engine tests. Also, in agreement with engine test results, iron tends to promote carbonization of some heavy lubricating oils in this oven test. In Examples 1 to 4, inclusive, set forth hereinafter, a typical Mid-Continent base'oil was used.

In these oven tests, the organic metal compounds formed residues of grayish-white oxides of the metals. In determining the amount of carbonaceous residue, formed by each oil sample which contained the organic metal compound, the amount of the metal oxide residue formed by an equal amount of the same compound by itself in the control was deducted from the total amount of residues formed by such oil sample, and the amounts fromhthe duplicate oil samples were averaged. In the examples, the residues, formed by the oil samples containing the chelates of this invention, were grayish-white like the metal oxides alone, and no carbonaceous material was observable on visual inspection.

In order to more clearly illustrate this invention, preferred modes of carrying it into eifect, and the advantageous results obtained thereby, the following examples are given in which the amounts are by weight except where otherwise specifically indicated:

EXAMPLE 1 Following the oven test procedure outlined hereinbefore, the eifect of various organic metal compounds on the combustion of 1.000 g. of lubricating oil was determined. The samples in tarred porcelain dishes, along with the appropriate controls on the oil (no added compound present) and on the compound itself, were held at 300 C. in a stream of air of 10 liters/ minute for one hour. The dishes were removed from the oven, allowed to cool and weighed. The amount of oil residue remaining, corrected for the residue contributed by the added compound, is a measure of the effectiveness of that compound in reducing the quantity of carbonaceous deposit formed by the oil. Results on the effect of divalentcobalt chelates of various salicylaldehyde-anils (and related compounds) on the decarbonization of the base oil at 300 C. are summarized in Table I, in which the residue is given as weight percent based on the oil sample:

. Table l OARBON-BURNING ACTIVITY OF COBALT (II) OH ELATE S IN LUBRICATING OIL AT 300 C.

Compound added to oil Residue From Oil,

Wt. (av

Test

, Cobalt (II) Chelate of Salieylaldehyde Sehifis Base of- Wt. Wt. Percen Percent Cpd. Co

011+ Com- 7 pound Oil Control m-nitroanlline p-nitroaniline Z-methoxy-B-nitroaniline.

2,4 dimethyl 5 ni troanlline.

B-nitro--t-butylaniline.

3-nitro-4-see-amylanilin e. 3-nitro-4-oetylaniline.

3-lnigro-4-dodeeylanie.

D -t-butylaniline see.-butylaminen-dodeeylamine n-octadecylamine.

EXAMPLE 2 The procedure of Example 1 was repeated using 0.454 g. of the cobalt (II) chelate of malonal-di(3-nitro-4-tbutyl)aniline suspended in 1,000 g. of the oil. At the end of one hour at 300 C., the quantity of residue produced from the oil containing the chelate was nil; while, in the control experiment (no chelate present) 16 weight percent of a characteristic carbonaceous deposite re- EXAMPLE 3 Following the test method and procedure of Example 1, the effect of various divalent-copper chelates of Schifis bases on the decarbonization of the base oil was. determined. Results on representative compounds are tabulated below (Table II). It will be evident from the data that presence of a nitro group is essential in copper chelates of salicylal-anilines and of malonaldiauilines.

Table II CARBON-BURNING ACTIVITY OF COPPER (II) CHELATES IN LUBRICATING OIL AT 300 C.

Compound Residue From Oil Wt. Percent (avg.)

Test

Copper (II) Chelate Wt. Wt. 011+ Oil of- Percent Percent Com- Control Cpd. Cu pound 1 Salicylal-(3-nitro-4-see. 66 6.3 0

butyl) aniline. 13 2 Salieylal-(3-nitro-4-oc- 39 3.15 1 13 tyl) aniline. 3 Salicylal-(p-t-amyD- 60 6. 3 23 15 aniline. 4 Sahcylal-n-dodecyl- 128 12.6 15 14 amine. 5 Salicylal-propylene- 31 6.3 30 15 1,2-diamine. 6 Malonal-di-(3nitro-4- 46 3.15 5 15 t-butyl) aniline. 7 Malonal-di-(p-t-amyl) 89 3.15 25 17 aniline. 8 4-Methylimino-2-bu- 26 6. 3 24 17 tanone.

l Commonly called N,Ndisalieylidene-1,Z-diaminopropane, 2 From tormylaeetone and methylamine.

It should also be noted that copper disalicylaldehyde itself showed no carbon-burning activity in the .above test.

EXAMPLE 4 Example 1 was repeated except that 0.656 g. of salicylal-(3-nitro-4octyl)aniline nickel (II), corresponding to 5.8 wt. percent of nickel, was suspended in the lubricating oil. At the end of one hour at 300 C., the quantity of residue produced from the treated oil was nil; whereas that from the untreated oil of the control was 15 weight percent of the original quantity of oil. In comparison, the nickel chelate of salicylal-n-dodecylamine showed no activity as a carbon-combustion catalyst, 16 weight percent residue being produced from both the untreated and the treated oil samples.

EXAMPLE 5 Salicylal-(3-nitro-4-t-butyl) aniline cobalt (II), in an amount to provide a concentration of 0.038 weight percent on the fuel, was added to a commercial gasoline containing tetraethyl lead. The treated fuel was evaluated in a Lauson engine under the following low-duty, cyclic engine conditions:

LOW-DUTY, CYOLIC LONAUS TEST Cycle 1 min. 3 min.

Speed 1,600 1, 730 Load, B.H.P 0 1 Fuel Flow, lbs/hr 1. 5

Air-Fuel Ratio 13. 551.5

Spark Advance BTDC 20 Coolant temp., F 212 Oil temp, F 175 Inlet air temp, F 150 The lubricant was a commercial base oil. The fuel had the following inspection data:

was interrupted periodically to determine the octane requirement of the engine, using primary reference fuels (blends of n-heptane and isooctane). After 92 hours operation, the requirement of the engine was 85 O.N. Upon completion of the test, the combustion chamber deposits were removed and weighed, amounting to 8.8 grams.

In a control run under identical conditions except that the above cobalt chelate was not present in the fuel, the requirement of the engine after 92 hours was 88 O.N. and the combustion chamber deposits amounted to 13.3

grams.

EXAMPLE 6 Salicylal-(3-nitro-4-octyl)aniline copper (II), was evaluated as a carbon-burning catalyst for jet fuels in a laboratory jet burner. The operating procedure consisted of burning 100 ml. of JP4 jet fuel containing 9.1 volume percent of l-methylnaphthalene at a fuel flow rate of 2.9 111l./1I1ll1. in which the primary air rate was 80.0 cu. ft./hr. and the secondary air rate 94.0

cu. ft./hr. Deposits, which accumulated on the inner walls of the stainless steel combustor and on the end section of the burner, were scraped off and weighed. When 0.02 weight percent of the above copper chelate was present in the jet fuel, the weight of the carbonaceous deposit was reduced by more than Similarly, 0.02 weight percent of salicylal-(3-nitro-4-sec.- amyl)aniline cobalt (II) or of salicylal-(3-nitro-4-octyl)- aniline nickel (II) in the above jet fuel resulted in 75% reduction in the quantity of carbonaceous deposit in the jet engine.

It will be understood that the preceding examples are given for illustrative purposes solely and that this invention is not limited to the specific embodiments described therein. On the other hand, it is apparent that many variations and modifications can be made without departing from the spirit and scope of this invention. For instance, the metal chelates, the proportions thereof, and the fuels employed can be widely varied, within the scope of the general description of the invention and as indicated therein.

From the preceding disclosure, it is apparent that this invention provides novel fuel compositions which contain very effective carbon-burning catalysts that prevent the formation, or greatly decrease the accumulation, of carbonaceous deposits in the combusion chambers of apparatus in which they are burned, such as spark ignition engines, diesel engines, jet engines, furnaces, oil burners, and the like. Such catalysts cause more complete combustion of the fuels and of carbonaceous materials normally formed during the combustion of the fuels. It is thus apparent that this invention solves, or at least greatly minimizes, serious problems involved in the combustion of normally liquid hydrocarbon fuels, and constitutes a valuable advance in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-metal chelate selected from the group consisting of cobalt, copper and nickel chelates of salicylaldehyde-nitroanils and cobalt and copper chelates of malonaldehyde-dinitroanils, each nitroanil portion of the molecule being an imino radical selected from nitrophenyl imino, alkyl-substituted nitrophenyl imino in which the alkyl radical contains 118 carbon atoms, and lower alkoxy-substituted nitrophenyl imino radical.

2. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-cobalt chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains l-l8 carbon atoms.

3. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-cobalt chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 18 carbon atoms.

4. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-cobalt chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted 3- nitrophenyl imino radical in which the alkyl radical contains 18 carbon atoms.

5. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-cobalt chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is a 4-alkyl-3-nitrophenyl imino radical in which the alkyl group contains 1-8 carbon atoms.

6. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of sa1icylal-(3-nitro- 4-t-butyl)aniline cobalt (II).

7. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-copper chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 1-18 carbon atoms.

8. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalent-copper chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 18 carbon atoms.

9. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by Weight of a divalent-copper chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is a 4-alkyl-3-nitrophenyl imino radical in which the alkyl group contains 18 carbon atoms.

10. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of salicylal- (3-nitro-4-ootyl)aniline copper (II).

11. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalentnickel chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 1-18 carbon atoms.

12. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalentm'cket chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 1-8 corbon atoms.

13. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalentiii nickel chelate of a salicylaldehyde-nitroanil in which the nitroanil portion of the molecule is a 4-alkyl-3-m'trophenyl imino radical in which the alkyl group contains l-8 carbon atoms.

14. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of salicyl-(3- nitro-4-octyl)aniline nickel (II).

15. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalentcobalt chelate of a malonaldehyde-di-nitroanil in which each nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 1-18 carbon atoms.

16. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalentcobalt chelate of a malonaldehyde-di-nitroanil in which each nitroanil portion of the molecule is an alkyl-substituted nitrophenyl imino radical in which the alkyl radical contains 1-8 carbon atoms.

17. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of a divalentcobalt chelate of a malonaldehyde-di-nitroanil in which each nitroanil portion of the molecule is a 4-alkyl-3- nitrophenyl imino radical in which the alkyl radical contains 1-8 carbon atoms.

18. A normally liquid hydrocarbon fuel containing from about 0.01% to about 1% by weight of the cobalt (II) chelate of malonal-di(3-nitro-4- t-butyl)aniline.

References Cited in the file of this patent UNITED STATES PATENTS 2,282,936 Chenicek May 12, 1942 2,346,662 Chenicek Apr. 18, 1944 2,346,663 Chenicek Apr. 18, 1944 UNITED STATES PATENT OFFICE CERTIFIQATE 0F (IQRR EGHN Patent No 2,891,853 June 23 1959 Edmund L, Niedzielski hat error appears in the printed specification It is hereby certified t correction and that the said Letters of the above numbered patent requiring Patent should readas corrected below.

Column 6, line 39, for "1,000 g of the oil" read w L000 g of. the oil column '7, line 25, for "LOW=DUTY, GYCLIC LONAUS TEST reed W 110W DUTY, CYCLIC LAUSON TEST column 9, line 30, for wicket read Signed and sealed this 3rd day of November 1959,

(SEAL) Attest:

KARL Ha AXLINE Attesting Oflicer RQBERT (I. WATSON Commissioner of Patents 

1. A NORMALLY LIQUID HYDROCARBON FUEL CONTAINING FROM ABOUT 0.01% TO ABOUT 1% BY WEIGHT OF A DIVALAENT-METAL CHELATE SELECTED FROM THE GROUP CONSISTING OF COBALT, COPPER AND NICKEL CHELATTES OF SALICYLADEHYDE-NITEOANILS AND COBALT AND COPPER CHELATES OF MALONALDEHYDE-DINITROANILS, EACH NITROANIL PORTION OF THE MOLECULE BEING AN IMINO RADICAL SELECTED FROM NITROPHENYL IMINO, ALKYL-SUBSTITUTED NITROPHENYL IMINO IN WHICH THE ALKYL RADICAL CONTAINS 1-18 CARBON ATOMS, AND LOWER ALKOXY-SUBSITUTED NITROPHENYL IMINO RADICAL. 